What Is Central Sleep Apnea? Atul Malhotra MD and Robert L Owens MD Introduction Control of Breathing The Concept of Loop Gain Types of Central Sleep Apnea Cheyne-Stokes Breathing Complex Apnea Sleep Transition Apnea Narcotic-Induced Central Apnea Hypoventilati on Syndromes Summary Central sleep apnea (CSA) describes a group of conditions in which cessations in air flow occur without respiratory effort. In contrast, obstructive sleep apnea patients have ongoing respiratory effort during respiratory events. However, considerable overlap exists in the pathogenesis and clinical presentation of ob- st ru ct iv e sl ee p ap ne a an d CS A. A go od wo rk in g kn ow le dg e of th e me ch an is ms un de rl yi ng CS A is impo rt an t fo r op ti ma l cl in ic al ca re. In ge ne ra l, CS A ca n be cl as si fi ed in to th ose wi th ex cess iv e dr iv e (e g, Ch ey ne -S to ke s brea thing ) versus those with inade quate drive (eg, sleep hypo venti latio n synd rome). One crit ical factor co nt ri bu ti ng to the ce ss at ion of ai r fl ow du ring slee p is th e co nc ep t of th e ap ne a thre sh ol d, su ch th at a P aCO 2 value below a certain level will lead to cessations in breathing. P aCO 2 can fall below the chemical apnea threshold when drive is excessive (eg, robust chemosensitivity) or when hyperventilation is occurring (eg, fol low ing aro usa l). An oth er imp ort ant fac tor is the los s of the so- cal led wa kef uln ess dri ve to bre ath e, suc h tha t so me ris e in P aCO 2 is likely to oc cu r at th e on se t of sl ee p. A va riet y of fa ct or s co nt ri bu te to th is ri se , in cl ud in g upper-airway collapse and diminished chemosensitivity (particularly during rapid-eye-movement sleep). In patients with low central drive, this further loss of drive at sleep onset can lead to marked hypercapnia in som e cas es. The tre atm ent of CS A is als o re vie we d in som e det ail , inc lud ing a ro le for pos iti ve air wa y pre ssure (eg , bi- level pos iti ve air wa y pre ssu re in hyp ove nti lat ion pat ien ts) and opt imi zat ion of me dic al the ra py (eg , in Che yne -St oke s bre ath ing ). A pau cit y of research exi sts in thi s are a, empha sizing the opp ort uni ties for you ng inv est iga tor s who are int er est ed in thi s fie ld. Key wor ds: cen tra l sle ep apn ea; CSA; ob str uctive slee p apnea; OSA; lun g; Che yne -St oke s bre ath ing ; slee p hyp ove nti lat ion syn dro me; sle ep; con tin uou s pos iti ve air way pre ssu re; CPA P. [Respi r Care 2010 ;55( 9):11 68–117 6. © 2010 Daedalus Enterprise s] Introduction Central sleep apnea (CSA) is defined by the cessation of air flow without respiratory effort. 1 This condition is in contrast to obstructive sleep apnea (OSA), in which on- goi ng resp irator y eff ort is pre sent durin g res pir ato ry events. 2-5 Although these definitions are quite distinct, in Rob ert L Owens MD and Atul Mal hot ra MD are aff ili ate d wit h the Divi sions of Slee p and Pulmonary and Criti cal Care, Depar tmen t of Medicine, Brigham and Women’s Hospital, Boston, Massachusetts. Dr Malhotra presented a version of this paper at the 45th RESPIRATORY CARE Journal Conference, “Sleep Disorders: Diagnosis and Treatment” held December 10-12, 2009, in San Antonio, Texas. Dr Malhotra has disclosed relationships with Philips, Pfizer, Merck, Apnex, Itamar, Sepracor, Cephalon, Sleep Group Solutions, Sleep HealthCenters, Medtronic, and Ethicon. Dr Owens has disclosed no conflicts of interest. Correspondence: Atul Malhotra MD, Division of Sleep, Department of Medicine, Brigham and Women’s Hospital, 75 Francis Street, Boston MA 02115. E-mail: [email protected]. 1168 RESPIRATORY CARE • SEPTEMBER 2010 VOL 55 NO 9